Process for storage properties of substantially sweet hydrocarbon distillates by treatment with alcoholalkali reagent



distillate and cracked oils for burner oils.

United States Patent PROCESS FOR STORAGE PROPERTIES OF SUB- STANTIALLY SWEET HYDROCARBON DIS- TILLATES BY TREATMENT WITH ALCOHOL- ALKALI REAGENT Raiph B. Thompson, Hinsdale, Ill., assignor to Universal Oil Products (Iompany, Chicago, Ill., a corporation of Delaware No Drawing. Application June 30, 1952, Serial No. 296,481

11 Claims. (Cl. 196-41) This invention relates to a novel method of improving the storage properties of substantially sweet hydrocarbon distillates and more particularly to a novel method of improving the stability of hydrocarbon distillates utilized for burner oil.

The term burner oil is used in the present specification and claims in a generic sense to include hydrocarbon distillates heavier than gasoline. These oils are marketed under various trade names such as fuel oil, furnace oil, heater oil, range oil, burner oil, diesel fuel, etc., and are selected to meet commercial specifications. In general, the burner oil will have an initial boiling point which may be as low as 300 F. or lower and an end boiling point which may range up to about 750* F. or higher.

In the past it has been the general practice to use as burner oils hydrocarbon distillates recovered from nondestructive distillation of petroleum oil and commonly referred to in the art as straight run distillates. With the increased availability of cracked oils in this boiling range, present practice is to utilize blends of the straight run The cracked oils are commonly referred to as cycle stocks, the term cycle stock being used because the burner oil is sepa rated from a fraction which is recycled to the cracking process for further conversion therein. Other sources of burner oil may include those produced by the reaction of carbon monoxide with hydrogen in the process known as the synthesis process, etc.

Because of the increasing amounts of catalytic cycle stock available at the present time, refiners have adopted the practice of blending the catalytic cycle stock with straight run distillate and/ or thermal cycle stock to produce burner oil. These blended burner oils tend to undergo discoloration and sediment formation to a greater extent than each of the constituents of the blend when used alone. It is apparent that discoloration of burner oil is undesirable because many burner oils are marketed on the basis of a color specification, and discolored oils cannot meet the color specification. Furthermore, even if they do meet the initial color specification but undergo discoloration in} storage, the burner oil becomes objectionable. Sediment formation in burner oil is objectionable because the sediment tends to plug strainers, burner tips, injectors, etc., and, when used as diesel fuel, tends to interfere with satisfactory operation of the engine. The sediment referred to herein is different from the solid material originally contained in burner oils and referred to in the art as B. S. & W. The sediment with which the present invention is concerned is not contained in the burner oil as produced but is formed during storage.

While the present invention is particularly applicable to the treatment of blends of catalytic cycle stock with straight run distillate and/or thermal cycle stock, there are cases where substantially sweet straight run distillates and/ or thermal cycle stocks, when used alone, will undergo excessive sediment formation and discloration in storage. It is understood that the present invention may be used for the purpose of retarding this deterioration. Sim- 2 ilarly, the present invention may be applicable to the treatment of substantially sweet lubricating oil, transformer oil, turbine oil, etc., which undergo excessive deterioration in storage.

As hereinbefore set forth, the present invention is particularly applicable to the treatment of sweet hydrocarbon distillates heavier than gasoline which are used as burner oils. However, the novel features of the present invention may be employed for the treatment of substantially sweet jet fuels which are unstable in storage. These jet fuels generally will have an initial boiling point within that of gasoline and an end boiling point above that of gasoline. Furthermore, the present invention also may be used for the treatment of gasoline or selected fractions thereof which are substantially sweet but are unstable in storage.

In the past it has been the practice to treat hydrocarbon distillates containing mercaptans with caustic, caustic methanol, or other alkaline treating reagents in order to reduce the mercaptan content of the hydrocarbon distillate. This treatment has been applied for the purpose of reducing the mercaptan content of the hydrocarbon distillate in order to produce a substantially sweet product and, therefore, to reduce the objectionable odor and corrosive properties of the distillate. Most catalytic cycle stocks are substantially sweet and, therefore, treatment with caustic has not been considered because the caustic treatment has been used for mercaptan removal and, since the sweet hydrocarbon distillate does not contain mercaptans, it would not be expected that treatment with the alkali would be of any advantage. Contrary to this expectation, I have found that the treatment of substantially sweet hydrocarbon distillates with a particular alkali-solvent solution does improve the storage properties of the substantially sweet hydrocarbon distillates. Furthermore, I have found that the use of the particular alkali-solvent solution possesses unexpected advantages over the use of the aqueous alkmi solution.

In one embodiment the present invention relates to a method of improving the storage properties of a substantially sweet hydrocarbon distillate which comprises treating said hydrocarbon distillate with an alkali-alcohol solution.

In a specific embodiment the present invention relates to a method of improving the storage properties of a substantially sweet catalytic cycle stock which comprises treating said cycle stock with caustic-methanol.

In another specific embodiment the present invention relates to a method of improving the storage properties of a blended burner oil which comprises treating a substantially sweet cycle stock with caustic-methanol, and blending the thus treated catalytic cycle stock with straight run distillate, whereby to produce a blended burner oil having improved storage properties.

Burner oils vary considerably depending upon the source of the crude oil from which the burner oil is derived. Because of these wide differences in burner oils, it has been found that different methods of treatment and/or the use of different additives appear to work satisfactorily with one burner oil but will be unsatisfactory when used for the treatment of other burner oils. Because of this difficult and pressing problem, the present applicant has made an extensive investigation of various methods of treating burner oils obtained from a number of different sources, and has found that the method of the present invention is a satisfactory solution for the treatment of burner oils containing substantially sweet hydrocarbon distillates. As hereinbefore set forth, this method of treating substantially sweet hydrocarbon distillates is a novel approach to the difficult problem, and the improved results obtained thereby normally would not be expected.

In accordance with the present invention, the substantially sweet hydrocarbon distillate is treated with an alkali-alcohol solution. Any suitable alkali reagent may be employed including sodium hydroxide, potassium hydroxide, etc. Similarly any suitable alcohol may be employed including methanol, ethanol, propanol, butanol, etc. Caustic-methanol is preferred and preferably is utilized as an aqueous solution thereof. The sodium hydroxide may be from about 20 to about 50 Baum and preferably from about 40 to about 50 Baum. The methanol employed may be anhydrous or it may contain varying amounts of water. However, as the water content of the methanol fraction increases, the concentration of the sodium hydroxide solution should be increased accordingly.

The amount of caustic-methanol solution to be employed will vary with the particular hydrocarbon fraction being treated and may range from 2 volume per cent of 100 volume per cent or more, based on the hydrocarbons to be treated, and the treatment may be effected in one or more stages. This treatment may be batch type in which the caustic-methanol solution is disposed in a vessel, and the hydrocarbon fraction is passed therethrough. Suitable means for effecting intimate mixing of the hydrocarbons and reagent solution preferably are provided and this may take the form of a suitable stirring device, bafiie plates, side to side trays, or the like in the treating vessel, and/ or recirculation of one or more of the hydrocarbon fraction or caustic solution by being pumped either within the treating vessel or out of and then back into the same. After the treatment has proceeded to the desired extent, a hydrocarbon phase is separated from a caustic-methanol phase, and this separation may be eifected in the same or different zone. The treated hydrocarbon phase will be of improved storage stability.

Treatment of the hydrocarbon fraction with the causticmethanol solution may be effected in continuous type operation, wherein the hydrocarbon fraction is passed counter-currently to the causticmethanol solution in either vertical or horizontal treating zones. These treating zones may contain baffie plates, bubble decks, side to side trays or other suitable contacting means. When a vertical treating zone is employed, it generally is preferred to pass the hydrocarbon fraction into a lower portion of the treating zone and to introduce the caustic and methanol, either together or separately, at a point or points higher than that to which the hydrocarbon fraction is supplied. When horizontal treating zones are employed, generally two or more of such zones are used. The hydrocarbon fraction to be treated is introduced into the first zone in the line of flow, and the caustic-methanol solution is introduced into the last zone in the line of flow. The hydrocarbon phase and caustic-methanol phase are each separately withdrawn from each zone and passed into the adjoining zone. The process flow and apparatus are well known in the art and require no detailed description in the present application because no novelty is claimed herein for a particular flow or type of apparatus per se.

The treatment of the hydrocarbon fraction with causticmethanol generally is effected at ambient temperature but in some cases elevated temperature may be employed, which temperature generally will not exceed about 200 F. After separation of the treated hydrocarbons from the caustic-methanol solution, the caustic-methanol solution may be treated in any suitable manner to regenerate the same and to recover the caustic and methanol for further use in the process. When desired, the treated hydrocarbons may be water washed to recover the slight traces of methanol when entrained therein or for any other desired puipose.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I -A West Texas catalytic cycle stock having an initial boiling point of about 380 F. was utilized for this example. This catalytic cycle stock was sweet by the doctor test. However, when stored at 100 F. for 14 days, the color of the cycle stock fell from an original value of 79 color to 0.5 color. The color was determined in a Lumitron, Model 402E Spectrophotometer. Distilled water is rated as 100 and a very dark oil is rated zero in this analysis. It will be noted that the catalytic cycle oil, even though sweet, fell from a color of 79 to a color of 0.5, which is definitely objectionable, and means that the oil will not meet the commercial color specifications.

Another sample of the catalytic cycle stock was treated with 10 volume per cent of a caustic-methanol solution, comprising 77% by volume of methanol and 23% by volume of 48 Baum caustic. After 14 days storage at 100 F., the caustic-methanol treated sample had a color of 64. It will be noted that the caustic-methanol treatment served to considerably improve the storage stability of the oil.

Another sample of the substantially sweet catalytic cycle oil was treated with 10 volume per cent of a 25% aqueous caustic solution. This treating reagent did not contain methanol. After 14 days in storage, the oil treated with caustic had a color of 37.2. It will be noted that the caustic treatment improved the color of the oil as compared to the untreated fraction but that this improvement was considerably less than that obtained by the caustic-methanol treatment. The considerably improved results obtained by caustic-methanol treating, in contrast to no treatment at all or as compared to the aqueous caustic treating, may be considered as somewhat surprising in view of the fact that the catalytic cycle stock was sweet to begin with and substantially no mercaptain removal was effected by this treatment. This novel process is of considerable importance for use in improving the storage stability of fuel oils.

EXAMPLE II The burner oil used in this example was a blend of 80% catalytically cracked cycle stock and 20% straight run distillate of a commercial No. 2 fuel oil. The catalytic cycle stock and the straight run distillate were each sweet. Different samples of this blended burner oil were treated in substantially the same manner as described in Example I. However, in addition to determining the color, the sediment was determined and is reported as mg. of sediment per 100 ml. of oil as obtained by filtering the sample of oil. As in Example I, the different samples of oil were stored at 100 F. for the number of days as indicated in the following table:

Table 1 Days Treatment None.

Color 62 0 0 Sediment; 0 4. 4 10. 6

Here again it will be noted that the caustic-methanol treatment of the fuel oil considerably improved the color as compared to the untreated or aqueous caustic treated samples.

Furthermore, it will be noted that the caustic-methanol treatment reduced the sediment formation to 1.3 which again is considerably improved as compared to that obtained by the aqueous caustic treatment.

EXAMPLE III The burner oil treated in this example was a thermal Table 2 Color after storage for following number of Treatment days None 32 27 Caustic-methanol t 66 67 68 Aqueous caustic 46 43 42 The above data further show the unexpected superiority of the caustic-methanol treatment as' compared to treatment with caustic in the absence of methanol.

EXAMPLE IV A doctor sweet straight run distillate for use as No. 2 fuel oil may be treated with volumes per 100 volumes of hydrocarbons of an aqueous solution of potassium hydroxide and ethanol. The treating solution may be of the following concentration: potassium hydroxide, 35% methanol and 30% water on a weight basis. This treatment may be effected at ambient temperature in a continuous flow operation in which the burner oil is introduced into the first of a series of three horizontal treating vessels and is passed successively through the second and third vessels, while the treating solution is introduced into the third treating vessel and is passed successively into the second and first treating vessels. The treated fuel oil fraction is washed with water in a fourth horizontal vessel. This treatment will serve to considerably improve the stability properties of the fuel oil.

EXAMPLE V A catalytic cycle oil may be treated with a caustic methanol solution comprising 25% by volume of 48 Baum caustic and 75% by volume of methanol. The thus treated catalytic cycle stock may be blended with a substantially sweet straight run distillate to produce a blended burner oil having improved storage stability. Discoloration of the blend Will be considerably retarded and the sediment formation will be considerably reduced as compared to a similar blend in which the catalytic cycle stock had not been treated with caustic-methanol.

EXAMPLE VI Substantially sweet straight run gasoline will be improved in storage stability by being treated with a caustic-methanol solution comprising 40% by volume of 48 Baum caustic and 60% by volume of methanol. This treatment may be effected at 80 F. by passing the gasoline into a lower portion of a vertical treating vessel, introducing the methanol at a mid-portion to said vessel and introducing caustic at an upper portion of the vessel. This method will serve to remove entrained methanol from the treated gasoline being withdrawn as an overhead stream from the treating vessel.

I claim as my invention:

1. A method of improving the storage properties of a hydrocarbon distillate substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said distillate with an alkali-alcohol solution.

2. A method of improving the storage properties of a hydrocarbon distillate substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said distillate'with a caustic-methanol solution.

3. A method of improving the storage properties of a burner oil substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said burner oil with an alkali-alcohol solution.

4.A method of improving the storage properties of a burner oil substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said burner oil with a caustic-methanol solution.

5. A method of improving the storage properties of a catalytic cycle stock boiling within the range of from about 300 to about 750 F. and substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said catalytic cycle stock with an alkali-alcohol solution, separating a treated catalytic cycle stock phase from an alkali-alcohol phase, and separately withdrawing each phase.

6. A method of improving the storage properties of a catalytic cycle stock boiling within the range of from about 300 to about 750 F. and substantially free of mercaptans but tending to undergo discoloration and sediment formation during storage which comprises treating said catalytic cycle stock with a caustic-methanol solution, separating a treated catalytic cycle stock phase from a caustic-methanol phase, and separately withdrawing each phase.

7. A method of producing a blended burner oil of improved storage properties prepared from a catalytic cycle oil and a straight run distillate oil, said oils boiling within the range of from about 300 to about 750 F. and being substantially free of mercaptans, which.

comprises treating at least one of said oils with an alkali-alcohol solution, separating a treated hydrocarbon oil from alkali-alcohol solution, and blending at least ailportion of the oil so treated with the other of said 0 s.

8. The process of claim 7 further characterized in that said alkali-alcohol solution comprises a causticmethanol solution.

9. The process of claim 7 further characterized in that the catalytic cycle oil and the straight run distillate are each treated with the alkali-alcohol solution prior to blending of the same.

10. The process of claim 3 further characterized in that said burner oil comprises a blend of catalytic cycle stock and said straight run distillate boiling in the range of from about 300 to about 750 F.

11. The process of claim 7 further characterized in that said blended burner oil also contains substantially sweet thermal cycle stock.

References Cited in the file of this patent UNITED STATES PATENTS 2,556,438 Parker et a1. June 12, 1951 2,585,284 Tom et al Feb. 12, 1952 2,592,383 Blatz Apr. 8, 1952 

1. A METHOD OF IMPROVING THE STORAGE PROPERTIES OF A HYDROCARBON DISTILLATE SUBSTANTIALLY FREE OF MERCAPTANS BUT TENDING TO UNDERGO DISCOLORATION AND SEDIMENT FORMATION DURING STORAGE WHICH COMPRISES TREATING SAID DISTILLATE WITH AN ALKALI-ALCOHOL SOLUTION. 